Adolescents with type 1 diabetes (T1D) must balance a complex daily treatment regimen while also facing the emotional, social and academic demands of this developmental period. Not surprisingly, adolescents are at increased risk for anxiety and depressive symptoms, poor coping and problem-solving skills, poor regimen adherence, and negative diabetes-specific health outcomes such as suboptimal glycemic control and recurrent diabetic ketoacidosis. Although a handful of psychological interventions targeting adolescents' poor behavioral and emotional functioning demonstrate beneficial effects on disease management and outcomes, no prevention programs exist that equip adolescents with behavioral skills and cognitive strategies shown to reduce both the risk of poor psychological functioning and the risk of negative health outcomes over time. Therefore, the proposed study will test whether a diabetes-specific adaptation of the Penn Resilience Program (PRP), a well-established program that demonstrates resilience promotion and depression prevention in healthy youth, is a viable candidate for a prevention program for adolescents with T1D. Our research team is in a unique position to conduct this research because we have adapted and pilot tested this program (PRP T1D). We will employ a randomized, controlled design and compare PRP T1D to an educational intervention (EI) on resilience characteristics, depressive symptoms, adherence behaviors, and glycemic outcomes. We will recruit 280 adolescents with T1D across two sites, measuring mediators (i.e., mechanisms of change) and outcomes at baseline, post-intervention, and at five surveillance visits spanning an additional 24 months. Our primary outcomes are prevention of depression and suboptimal glycemic control. Further, we will evaluate whether resilience and behavioral adherence function as mechanisms of change for our primary outcomes. The potential impact of this study is not only in preventing depression in this high risk population of youth with T1D, which is dangerous and costly by itself, but also in preventing suboptimal glycemic control, a common, expensive, and dangerous problem in T1D. By preventing depression, we alter dangerous trajectories toward nonadherence and poor health outcomes. Further, the intervention builds resilience skills which serve as protective mechanisms for improving health outcomes. Very few preventive intervention models have been tested, and none exist for this high risk group of youth with T1D. Results from this study will break new ground in the scientific understanding of the mechanisms of prevention in T1D and should reduce the staggering costs of clinical care and prevent complications in the future. In addition, our results will be generalizable to other pediatric chronic conditions which show similarly robust associations between depression and negative health outcomes. Our research team is uniquely positioned to carry out this research as we have complimentary expertise in conducting RCTs, we are integrated in to multidisciplinary teams with strong infrastructures to promote success in our work, and we have substantial clinical experience and expertise with this population.